1. Field of the Invention
The present invention relates to a printing apparatus for printing image information on a printing medium, a printing cartridge to be mounted to the printing apparatus, and a colorant container.
2. Description of the Related Art
Generally speaking, in an ink jet printing apparatus in which ink is ejected from a plurality of printing elements as droplets to form an image on a printing medium, a distance between an ink ejection surface of an printing head and the printing medium (hereinafter merely referred to as “paper distance”) largely effects upon image quality. For example, the ejecting direction of ink droplets ejected from a plurality of printing elements arranged on the printing head slightly scatters by all means. Also, a scanning speed of a carriage carrying the printing head somewhat varies. In such a case, a landing point of the ink droplet varies on the printing medium, and an amount of the variation becomes larger as the paper distance increases to deteriorate the image quality. On the other hand, however, if the paper distance is excessively short, there is a risk in that the ink ejection surface may be brought into contact with the printing medium due to the undulation of the printing medium. Accordingly, in an area in which the printing head carries out the printing operation, the printing medium is preferably in a tense state to maintain the paper distance within a predetermined range.
FIG. 1 is a sectional view for explaining a structure of a conventional ink jet printing apparatus in the prior art.
In FIG. 1, reference numeral 11 denotes a pickup roller; 13 denotes a printing medium; 12 denotes a paper-feed tray for carrying a stack of non-printed printing media 13; 14 denotes a feed roller; 15 denotes a pinch roller; 16 denotes a platen; 17 denotes a cartridge in which ink tanks and a printing head are integral with each other; 18 denotes a delivery roller; 19 denotes a nip roller; and 20 denotes a paper-delivery tray.
When a command for commencing the printing operation is given by a host computer or others, the pickup roller 11 begins to rotate in the direction indicated by an arrow in the drawing (in the clockwise direction) to feed the printing medium 13 one by one from the topmost of the stack in the paper-feed tray 12. Thereafter, the printing medium 13 is conveyed while being nipped between the feed roller 14 and the pinch roller 15 and reaches an image printing section on the platen 16. The printing operation is carried out by ejecting ink in accordance with image signals from the respective printing elements in the printing head while reciprocating a carriage (not shown) in the direction vertical to a paper surface of the drawing. The printing medium 13 on which the image has been printed is conveyed outside from the apparatus while being nipped by the delivery roller 18 and the nip roller 19 and placed on the paper-delivery tray 20.
Axial centers of the feed roller 14 and the pinch roller 15 are on the same straight line extending in the vertical direction. This is also true to those of the delivery roller 18 and the nip roller 19. Further, a paper-passing surface (upper surface) of the platen 16 and a contact area of the feed roller 14 with the pinch roller 15 are in the same plane so that the feed roller 14 conveys the printing medium 13 in the horizontal direction. Also, the paper-passing surface (upper surface) of the platen 16 and the contact area of the delivery roller 18 with the nip roller 19 are in the same plane so that the delivery roller 18 conveys the printing medium 13 in the horizontal direction.
Generally speaking, regarding the feed roller 14 and the delivery roller 18, the peripheral velocity is larger in the delivery roller 18 than the feed roller 14 so that the printing medium 13 is conveyed while being pulled by the delivery roller 18. On the other hand, a conveying force of the delivery roller 18 is selected to be sufficiently smaller than that of the feed roller so that the delivery roller 18 pulls the printing medium 13 while sliding in fact on the delivery roller 18. By imparting the printing medium 13 with a proper tension in such a manner, it is possible to flatten the printing medium 13 so that the paper distance d is maintained constant between the ink ejection surface of the ink cartridge 17 and the printing medium 13. Generally, the paper distance d is suitably in a range from approximately 0.7 to 1.2 mm. If it is maintained within this range, there is no influence of the variance in the landing point described above, and the ink ejection surface is prevented from being in contact with the printing medium due to the undulation of the printing medium.
Recently, there has been the requirement for the ink jet printing apparatus to increase the printing speed and reducing the running cost. To realize the speed-up of the printing operation, it is preferable to increase the number of printing elements arranged on the printing head so that a printing width h is widened during one printing scan of the carriage. Also, to reduce the running cost, the enlargement of an ink tank is effective for increasing an amount of usable ink. However, in either case, a size becomes large in the printing apparatus of the conventional type. That is, if the printing width h is widened, a region H between the feed roller 14 and the delivery roller 18 must be also widened to increase the lengthwise dimension of the printing apparatus as whole. On the other hand, to increase the amount of usable ink, it is necessary to enlarge the ink tank, which in turn needs the elongation of the ink tank and the printing apparatus in the height direction relative to the printing region.
In peripheral instruments of a personal computer used around a desk, a thin and vertical type is now being a main trend. For example, a CRT display is replaced by a liquid crystal display, and a personal computer becomes thin and compact to be capable of being comfortably placed on a corner of the desk. Further, in a flat head scanner, a slim type used in the vertical position is being a main trend. In such a situation, the above-mentioned trend is also true to a personal ink jet printing apparatus used around the desk, and a thin and compact type used in the vertical position is required. Accordingly, such a trend contradicts the requirement for the high speed printing and the reduction of running cost which result in the size-enlargement of the apparatus as described above.